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Effects of Different Organic Acids in Iron Removal from Kaolin Ore
Abstract
To reduce the iron content of kaolin to the desired levels, a variety of industrial physical and chemical processes are employed in practice. Though the physical methods (classical magnetic separation, new and more expensive super conductive magnetic separation in particular) are extensively used, generally low efficiency of these methods has led to the search for alternative chemical methods for the removal of iron, which have gained importance recently. In this study, the chemical removal of the iron impurity present in kaolin supplied by ÇİMSA Inc. was investigated by using organic acids. The effect of parameters including the type of organic acids, temperature, pulp density, leaching time and reagent concentration on the extent of iron removal were investigated applying factorial design ANOVA-Yates test technique for the statistical analysis of the results. Under optimum condition (10% pulp ratio, 40 g/L of oxalic acid concentration, 90°C temperature and 120 minutes of leaching (reaction) time), the removal of Fe2O3 was obtained as 34.45% for oxalic acid leaching.
... Chemical beneficiation methods make use of leaching, usually under acidic or reducing conditions (Veglio & Toro, 1994;de Mesquita et al., 1996;Ambikadevi & Lalithambika, 2000;Atkinson & Fleming, 2001). Therefore, numerous leaching agents such as organic acids (de Mesquita et al., 1996;Veglio et al., 1996;Ambikadevi & Lalithambika, 2000;Tuncuk et al., 2010;He et al., 2011), sulfuric acid (H 2 SO 4 ; Veglio, 1997;Tuncuk et al., 2013), sodium dithionite (Na 2 S 2 O 4 ; Mehra & Jackson, 1958;Thurlow, 2001;Gougazeh, 2018), sodium thiosulfate (Na 2 S 2 O 3 ; Olvera-Venegas et al., 2017), thiourea (H 2 NCSNH 2 ), dioxide thiourea ((NH 2 ) 2 CSO 2 ; Veglio, 1997;Xia et al., 2012;Lu et al., 2017aLu et al., , 2017b, chlorine water (Carpmael, 1928;González & Ruiz, 2006) and EDTA (Borgaard, 1979), as well as thermochemical techniques (Khalifa et al., 2013(Khalifa et al., , 2019, have been used to remove iron and other impurities from quartz and clay minerals. The bioleaching technique (Kostka et al., 1999;Lee et al., 2002;Cameselle et al., 2003;Hosseini et al., 2007;Guo et al., 2010;He et al., 2011;Zegeye et al., 2013) is also of great interest for iron removal from clay minerals. ...
... Among the organic acids used as effective solvent reagents, oxalic acid (C 2 H 2 O 4 ) has been the most promising (Panias et al., 1996a;Calderon et al., 2005;Lee et al., 2006Lee et al., , 2007Martínez-Luévanos et al., 2011;Hernandez et al., 2013;Baba et al., 2015;Taran & Aghaie, 2015) because of its high reducing power, complexing capacity and acid strength (Panias et al., 1996a;Nwoye et al., 2009;Tuncuk et al., 2010;Barrachina et al., 2017). Moreover, when using oxalic acid, the dissolved iron can precipitate as ferrous oxalate from the leaching solution and can be further reprocessed to recover the oxalic acid (Taxiarchou et al., 1997;Yu et al., 2012;Liu et al., 2019;Schapiro et al., 2020). ...
This study reports a leaching process along with a novel physical pretreatment technique to remove iron impurities from kaolin using oxalic acid. A detailed examination of the physical properties of the minerals confirmed that almost none of the leaching-resistant iron oxides, specifically hematite, was completely interlocked with the clay minerals. Accordingly, a pre-agitating technique followed by high-pressure washing of the sample on a 600 μm sieve were applied. In this method, by discarding up to 20% of the raw material, >54% of the total iron content of the raw kaolin was removed, and the iron content was reduced from 9.75% in the initial sample to <6.00% in the passing fraction. Application of this pretreatment method rendered the leaching process successful at 97°C using 0.3 M oxalic acid solutions for 1 h under atmospheric pressure. Compared to the leaching of the raw material without pretreatment, which consumed at least 0.5 M oxalic acid over a minimum period of 2 h, the method used was very cost-effective and favourable, reducing the iron content of the product to <1% and producing high-quality kaolin.
... Ambikadevi and Lalithambika (2000) evaluated the effectiveness of several organic acids (acetic, formic, citric, ascorbic acids etc.) to dissolve iron from iron compounds. Oxalic acid was most promising because of its acid strength, good complexing characteristics and high reducing power, compared to other organic acids (Nwoye et al., 2009;Tuncuk et al., 2010). ...
In the present study, to investigate the effects of acidic leaching on the iron removal from kaolin clay supplied by Cam-Ser Madencilik A.S., the 24 full factorial design of experiments and analysis of variance (ANOVA) were performed. The aim of the initial phase of research was to determine the effects of the main and interaction factors which can potentially influence the iron removal process. The factors were; pulp density, sulfuric acid concentration, temperature, leaching duration and reducing agent (oxalic acid, citric acid and hydrogen peroxide) concentration. The highest iron extraction yield (IEY) (26.3%) was obtained after 120 min of treatment at 90 °C, 20% pulp density, 3 M H2SO4 and with 0.50 M H2O2 as a reducing agent. For the purpose of increasing the IEY, in the second phase of research, initially the particle size of the kaolin sample was decreased to − 106 μm providing the liberation of iron oxides. Then, two-step leaching experiments were carried out with the optimum leaching conditions of full factorial design tests. The maximum IEY was 37.0% after two-step leaching with the optimum conditions of H2SO4 and H2SO4 with oxalic acid leaching. Iron oxide content of kaolin clay was decreased from 2.40% to 1.51%.
The chemical and mineral compositions of bauxite recovered from the Severoonezhsk Bauxite Mine (Arkhangelsk region, Russia) were studied by XRD, ICP-OES, TG/DSC, SEM, TEM, and Mössbauer spectroscopy. The iron-containing minerals of the bauxites were found to comprise alumogoethite (α-Fe1–xAlxOOH), alumohematite (α-(Fe1–xAlx)2O3), alumoakaganeite (β-Fe1–xAlxO(OH,Cl)), and chromite (FeCr2O4). The efficiency of Fe extraction from the bauxite by HCl leaching was 82.5% at 100 °C, HCl concentration of 10%, solid/liquid ratio of 1:10, and the process duration of 60 min, with aluminum loss from the bauxites below 4.5% of the total Al contents in the bauxite. Analysis of the kinetics of the iron leaching process proved diffusion to be the limiting stage of the process at 90–100 °C. Bauxite residue after leaching presented traces of α-Fe1–xAlxOOH and β-Fe1–xAlxO(OH,Cl), and most of the iron content was in the FeCr2O4. In bauxite residue after HCl leaching, in addition to iron oxide, the contents of chromium and calcium oxides significantly decreased. The iron chloride liquor after leaching contained the rare earth elements (REE) of 6.8 mg/L Sc, 4.1 mg/L Ce and 2.3 mg/L Ga.
Purification of quartz (iron in particular) with chemical prosesses is extremely important for many industries including glass, electronic, detergent, ceramics, paint, refractory and metallurgy. The iron content of quartz is required to be in the range of 0.01-0.1% for its industrial use. Turkish quartz reserves have not been exploited effectively in the glass and electronical industries mainly due to the limitations in the quality and quantity of these resources. There appears to be different physical and chemical methods in industrial scale available for the beneficiation of quartz to reduce its iron content down to the desired levels. Although the physical methods including conventional magnetic separation, new and more expensive super conductive magnetic separation and flotation are commonly employed, the chemical methods have been gaining importance particularly due to the low efficiency of physical methods for iron removal. Iron as the most significant impurity present in quartz ores can be substantially removed by aqueous chemical processes using organic and inorganic acids. In this respect, oxalic acid appears to be one of the most significant leaching reagents for the removal of iron. In this article, the industrial use of quartz, area specific requirements for product quality and chemical methods (with particular reference to oxalic acid systems) used in the purification of quartz are critically reviewed.
Kaolin available in Deopani, Assam of northeastern region of India was characterized by FTIR, XRD, DTA and by wet chemical analysis methods. The major impurities in the clay are quartz and siderite. Wet sieving of the clay by −53-μm sieve removes almost all the quartz and a major amount of Fe bearing impurities. The iron content of the clay may be reduced further by treating with wet high intensity magnetic separator (WHIMS) or leaching with organic acids. The effectiveness of various leachants follows the order: Oxalic>Oxalic+EDTA>Malonic>Citric acid. Almost all the nonstructural iron may be removed at room temperature by using 0.4 M oxalic acid solution. The leached clay may find use as a ceramic raw material and filler material for paper and other materials.
Model for predictive analysis of the quantity of heat absorbed by oxalic acid solution during leaching of iron oxide ore has been derived. It was observed that the validity of the model is rooted in the expression (lnQ)/N = √T where both sides of the relationship are correspondingly almost equal. The model was found to depend on the value of the final solution temperature measured during the experiment. The respective deviation of the model-predicted Q values from the corresponding experimental values was found to be less than 21% which is quite within the acceptable range of deviation limit of experimental results. The positive values of heat absorbed as obtained from experiment and model indicate and agree that the leaching process is endothermic in nature.
ZET Kaolenlerin safsızlaştırılması, içeriğindeki demirin kimyasal ve biyolojik yöntemlerle uzaklaştırılıp öncelikli olarak kâğıt, seramik, boya, refrakter, plastik sanayilerinde kullanılabilecek hale getirilmesi açısından önemlidir. Kaolenler seramik ve kâğıt sanayinin en önemli hammaddesidir. Kaolen demir içeriğinin endüstriyel proseslerde kullanılabilmesi için belirli oranlarda (en fazla %0,4-0,5) olması gerekmektedir. Özellikle ülkemiz kaolenlerinin demir içeriğinin yüksek olması (%1'in üstünde) nedeniyle, %90'ın üzerinde beyazlık indeksi istenen kâğıt ve seramik sanayinde kullanılamamaktadır. ABSTRACT Purification of kaolins i.e. removal of iron with physical, chemical and biological methods is important for their use mainly in paper, ceramics, paint, refractory, and plastic industries. Kaolin is the most important raw material of ceramics and paper industries where its iron content must be less than 0.4-0.5%. Especially, because of the high iron content of Turkish kaolins (>1%), they cannot be used in the paper and ceramics industries for which >90% whiteness index is required. By using organic acids such as oxalic, gluconic, citric, asetic, formic, ascorbic, succinic, tartaric and malonic acids, iron found in kaolin as an impurity is chemically removed. Biological methods may be used as an alternative to the chemical methods. Purification of kaolin using the biological methods are based on the activities of Aspergillus nigeras fungus and Bacillus and Pseudomonas as bacteria to produce high level of organic acids. In this article, the importance of chemical and biological methods and the application areas of kaolin are critically reviewed.
The removal of iron from silica sand with oxalic acid has been studied under various experimental conditions in order to optimise the process parameters and reach a high degree of iron removal at minimum operating cost. The parameters studied were: temperature, pH of the solution, oxalate concentration, Ar purging, and ferrous ions addition to the solution. For the specific silica sand sample used, at temperatures varying between 90–100°C the maximum iron extraction that can be achieved is approximately 40%. At temperatures lower than 80°C this extraction is decreased to 30%. At these temperatures purging of the oxalate solution with Ar and ferrous ions addition has no effect on the iron extraction, while at temperatures lower than 25°C iron dissolution is accelerated with the addition of ferrous ions. Iron dissolution is significantly affected by the pH, while it is practically independent of the oxalate concentration and the pulp density. Without the addition of bivalent iron, iron extraction is optimised in high acid solutions; when ferrous ions are added in the oxalate solution, best results are achieved at pH 3.
The oxidation state of Fe in the crystal structure of clay minerals plays an important role in determining the chemical and physical properties of the clay. These properties, among which are swelling, cation exchange capacity, and hydraulic conductivity, affect the fertility, strength, and porosity of agricultural soils and influence the fate and behavior of pollutant chemicals such as heavy metals and pesticides in soils and sediments. In natural systems, bacteria may be the most significant cause of Fe reduction in clay minerals.
Heterotrophic acid-producing bacteria and fungi were used to remove iron from quartz sands. The best results were achieved by a strain of Aspergillus niger, which produced culture solutions in which the oxalic and citric acids were the main components. A two-stage process was developed in which sands were leached at 90 degree C with lixiviant produced as a result of the cultivation of the strain at 30 degree C. The study aims at elucidating possibilities to decrease, by means of bio-leaching, the iron content of some sands to a level which will make them suitable for the manufacture of high-quality glass.
In the present study a bleaching process of a kaolin of industrial interest was carried out using thiourea as the leachant agent in the iron removal process. The beneficiation of kaolin, by iron removal, improves its economic value, and it is then possible to use it in the ceramic and paper industries. The effect of thiourea was investigated together with other factors, such as sulphuric acid concentration, temperature and treatment time. Full factorial experiments were performed to determine the main and interaction effects on the iron dissolution from the mineral: the largest iron extraction yield (94%) was obtained after 150 min. of treatment at 90°C, 0.25 M H2SO4 and with 10 g/l of thiourea. At the same temperature the iron extraction yield was 68% after 120 min. of treatment with 0.1 M H2SO4 and 1 g/l thiourea. An empirical model of data fitting was used in order to evaluate the optimal conditions of the process, considering as factors the treatment time and the thiourea concentration. The experimental results show the technical feasibility of this process for the removal of iron from kaolin used in the experimental tests.
Kaolin is mostly associated with minor quantities of ancillary minerals containing transition elements such as iron and titanium. These ions impart color to the white kaolin which adversely affects its application in paper and paint industries. Hence their removal is of prime importance in the optimum utilization of kaolin. The coloring effect as well as the mode of removal of these impurities depends on the “species” of the ion and/or the type of mineral. The present paper deals with the investigation on two Indian kaolins of different geological origin, one from Gujarat state at the western part of India and the other from Kerala State at the southern most part. Detailed physical, chemical and mineralogical characterization of the samples was carried out. The product clays after beneficiation by size classification, high gradient magnetic separation and chemical leaching were found to be of acceptable grade for paper industry with respect to optical properties and particle size. The impurity minerals were concentrated by different methods so that their identification was easier. Attempts were made to study the Fe species by correlating the XRD, chemical assay, DCB treatment and EPR spectral information of the clay samples before and after beneficiation. Iron stained anatase was found to be the major impurity in the Gujarat clay whereas iron was present as oxide/hydroxide in the Kerala sample. The beneficiated products from the Kerala clay were found to have better optical properties.
The effect of various organic acids viz. acetic, formic, citric, ascorbic, succinic, tartaric and oxalic acids, on the iron removal and the resulting brightness improvement of an iron-stained kaolinitic clay from Kalliyur, Thiruvananthapuram, South India, has been investigated. Oxalic acid was found to give the best results both at room temperature as well as at high temperatures because of its high acid strength, good complexing capacity and reducing power. The reaction parameters such as time, temperature and reagent concentration were optimised. The optimum conditions required for achieving brightness ≥80% were: temperature — 100°C, oxalic acid concentration — 0.1 M and reaction time — 90 min. The leaching tests at room temperature for 30 days improved the brightness from 66.3 to 83.5% ISO. The corresponding iron oxide removal was of the order of ∼80%. The addition of ferrous ions and protons improved the reaction kinetics. The leaching tests carried out on previously beneficiated samples using magnetic separation showed only a slight improvement in brightness indicating that brightness depended more on the surface coated iron oxides rather than on the discrete particles. The effect of acid leaching on the physical properties of the clay such as brightness, plasticity, viscosity, specific surface area and pore volume were compared. The slight increase in the specific surface area and the pore volume are suggestive of removal of the cementing non-crystalline alumina, silica and iron oxides from the clay surface and also due to the resulting delamination to a limited extent. No marked change was observed in the viscous as well as the plastic properties due to the deferration treatments.
Goethite dissolution studies were carried out using a statistical design of experiments, and process parameters were further optimized. A regression equation for the dissolution of iron was developed as a function of four parameters (acid concentration, temperature, ascorbic acid concentration and time). All the parameters were varied at two levels for designing experiments and six base level experiments were also carried out to estimate error and standard deviation. The dissolution process was further optimized by the method of steepest ascent using the results of statistical design of experiments.
Bleaching of kaolin with a high content of iron oxides by means of three organic acids (citric, gluconic and oxalic) was studied. The first two release small quantities of iron oxides from the kaolin, which means they will not be adequate for large-scale processes. Oxalic acid is capable of dissolving all the leachable iron in kaolin, reaching a whiteness index of 80%, thus making the kaolin suitable for its basic industrial applications. ©1997 SCI
The removal of iron from kaolin of industrial interest by acid leaching under pressure, using sucrose as reductive substance, has been studied. Several factors have been taken into consideration in the experimental runs planned, using an experimental design technique: acid concentration (H2SO4), sucrose concentration (C12H22O11), temperature and time of treatment. The experimental tests were performed using industrial mineral concentration (30% w/v) in an autoclave device. The main effects and the significant interactions involved in the leaching process were found by ANOVA; a significant improvement in iron removal was obtained due to the presence of sucrose. Some considerations about the mechanism of the process have been made considering the behaviour of the carbohydrates in hot acid solutions. Furthermore, sequential leaching tests were carried out in order to examine the possibility of recycling leach solutions for the treatment of non-treated mineral. A methodological approach is shown in the study of leaching processes using factorial experiments instead of experiments changing “one factor at a time”. The experimental results demonstrate the possibility of using carbohydrates in the bleaching process of minerals of industrial interest.
The purpose of this study was to investigate the impact of redox-induced changes in the organization of the clay fraction of a bulk vertisol using transmission electron microscopy. Chemical and X-ray powder diffraction (XRD) analyses indicated that the oxidized clay was composed of 32% kaolinite and 68% non-pure smectitic material, mostly a dioctahedral beidellite with octahedral Fe, according to Quantarg2 and DecompXR models.
The cation exchange capacity of the soil increased from 26.1 to 65 cmol c ⁺ kg ⁻¹ due to structural iron (Fe Str ) reduction and dissolution of oxide coatings. Transmission electron micrographs revealed dramatic changes upon reduction. Oxides were dissolved and the smectite increased in particle darkness, lateral extension, thickness, compactness and stacking order. These changes were interpreted to be a consequence of sorption of ferrous Fe and reduction of Fe Str , as found in previous studies on pure Fe-bearing smectites.
The aim of the work was to decrease the iron content of ferrous quartz sands by fixed-bed column leaching with recycling of the leaching solutions in order to attain a product suitable for industrial use. Dissolution of iron was achieved by treating the sands in an acid medium with a reducing agent (oxalic acid) to convert FeIII into FeII.The factors assumed to affect dissolution of iron, such as temperature, oxalic acid concentration, pH and flow-rate, were studied with a 24 full factorial design in order to assess the main effects and the interactions among the factors.Removal of 46.1% iron gives a product containing 0.0163% Fe2O3 which is fit for industrial applications.
From the Publisher:This well-respected text is designed for the first course in probability and statistics taken by students majoring in Engineering and the Computing Sciences. The prerequisite is one year of calculus. The text offers a balanced presentation of applications and theory. The authors take care to develop the theoretical foundations for the statistical methods presented at a level that is accessible to students with only a calculus background. They explore the practical implications of the formal results to problem-solving so students gain an understanding of the logic behind the techniques as well as practice in using them. The examples, exercises, and applications were chosen specifically for students in engineering and computer science and include opportunities for real data analysis.
In the present work the removal of iron, present as impurity in a kaolin of industrial interest, was performed. An effective iron reduction using microbial mixed cultures was attained (up to 81%) while a significant iron reduction in the presence of single microbial cultures was achieved (up to 37%).The active microorganisms belong to the genera Bacillus and Agrobacter. The enzymatic and un-enzymatic iron reduction was evaluated.Finally the molasses as carbon source for heterotrophic bacteria were succesfully tested.
In view of an industrial application of hydrometallurgical processing of kaolins of industrial interest, samples of this mineral have been treated in an acid medium with a reductive agent (sucrose) in order to improve its iron extraction. The basis of this process is the ferric iron solubilization and its reduction to ferrous iron to improve the iron removal in acid medium. In this manner it is possible to exploit the commercial value of the iron-containing kaolins. In this work the main factors that can influence the iron extraction, in order to obtain iron-free kaolins using a treatment at atmospheric pressure, have been tested using factorial experiments. Best results have been obtained using the following experimental conditions: iron removal of 98% at 90°C in 100 minutes with 1 M H2SO4, 4 g/l sucrose hydrolysed and 200 rpm.
In the present work a preliminary study of iron removal from a yellow kaolin supplied by ECC International (Europe) Ltd. was performed using mainly oxalic and ascorbic acids in sulfuric acid solutions. The aim of the initial phase of research was to determine the effects of the main factors which can potentially influence the iron-removal process. Two-level fractional factorial experimentation was thus utilized to establish the main factors having an influence on the iron removal and to define a subsequent experimental test design. The factors involved in this study were: temperature, concentration of oxalic and ascorbic acids, mineral concentration, mixing conditions, and concentration of the sulfuric acid. The experimental results shown that the effect of oxalic and ascorbic acids and of the temperature are the most important. In the investigated conditions, the maximum iron extraction yield was 43−45% after 3−4 h of treatment indicating a limit of iron removal for the mineral. Further study is in progress to define the best operative conditions considering the economic point of view.
Reactions between kaolin and inorganic salts, such as sodium hydrogen sulfate and ammonium sulfate, or inorganic acids, such as hydrochloric acid and sulfuric acid, can be focused either on the production of Al or on the adjustment of the silica-to-alumina ratio of the kaolin. On the basis of adjusting the silica-to-alumina ratio, kaolin and ammonium sulfate [(NH4)2SO4] are mixed and heated in a furnace at temperatures between 200 and 1000 °C. The parameters studied were the reaction temperature and time, the proton-to-alumina molar ratio, the calcination temperature and time, and the reaction atmosphere. The products of the reaction between kaolin and (NH4)2SO4 were characterized by means of X-ray diffraction (XRD). The Al reaction yield grew until reaching a maximum at 600 °C and started to decrease sharply beyond this temperature. The Ti reaction yield values were lower than the Al reaction yield values, showing a maximum at 600 °C and decreasing smoothly as the reaction temperature was increased. The Fe reaction yield exhibited the same tendencies as the Al reaction yield. With regard to the proton-to-alumina molar ratio, a maximum in Al, Ti, and Fe reaction yields was observed at rH = 3. Precalcination of kaolin produced only slight decreases in the Al and Ti reaction yields and a slight increase in the Fe reaction yield. The products of the reaction were triammonium hydrogen disulfate [(NH4)3H(SO4)2], ammonium aluminum sulfate [NH4Al(SO4)2], aluminum sulfate [Al2(SO4)3], and alumina [Al2O3]. Brunauer−Emmett−Teller (BET) specific surface area tests indicated an increase of the BET specific surface area for short reaction times, reaching values above 200 m2/g.
The dissolution of metal oxides is a process of importance in several fields such as hydrometallurgy, passivity of metals, and cleaning of boilers and metal surfaces in general. Oxalic acid is one of the most effective reagents for dissolution of magnetite under mild acid conditions. Magnetite is the oxide that confers passivity to steel surfaces. In the present communication, the more salient features of the mechanism of dissolution of magnetite by oxalic acid solutions are discussed with special focus on the role played by ferrous ions in the process. Oxalate plays an unique role among complexing carboxylic ligands in the dissolution of magnetite; it not only facilitates the electron-transfer reaction but also mediates in a relatively fast dissolution during the initial induction period (the induction period is much shorter than in the case of the dissolution of magnetite by ethylenediaminetetraacetic or nitrilotriacetic acid). This unique role has been used in the development of a very efficient scale removal formulation used in the decontamination of nuclear power plants.
Four metakaolins were prepared by calcination of a natural Spanish kaolin (Navalacruz deposit, Zamora province) at 600, 700, 800, and 900 °C. These four metakaolins, more reactive than the parent kaolin, were submitted to acid and alkaline activations. Acid activation was carried out with 6 M HCl at room temperature and at 90 °C under reflux conditions, with times of treatment of 6 and 24 h. Treatment at room temperature did not produce any alteration in the structure or in the properties of the metakaolins. Treatment under reflux conditions for 6 h led to the removal of most of the octahedral Al3+ cations, and the formation of an amorphous silica phase, with surface area up to 219 m2/g, because of a high development of both the internal and the external surface of the solids. Acid treatment under stronger conditions (reflux, 24 h) also removed the octahedral cations, but provoked an amorphization of the silica obtained (S ≈ 23 m2/g). The metakaolin prepared by calcination at 900 °C showed a lower reactivity than those synthesized at the other temperatures considered. The alkaline treatments were carried out with 1 M and 5 M KOH solutions, the treatments with the concentrated solution, both at room temperature and, especially, under reflux, led to the dissolution of the metakaolins and to the formation of well-crystallized K−F zeolite. The solids obtained by acid treatments are promising as adsorbents and catalyst supports, while treatment in alkaline conditions may be a good method for preparing K−F zeolite.
Second derivative diffuse reflectance spectroscopy (DRS) in the visible range has been used to characterize changes in colour and identify the nature of Fe oxides which withstand reduction during experimental yellowing of reddish materials. It is accepted that haematite dissolves preferentially and faster than goethite, and Al-substitution controls the dissolution kinetics of Fe oxides. However, DRS has shown that haematite is more resistant than predicted and that some Fe-oxides, probably trapped within kaolinite particles, are inaccessible to solvents. DRS allows the nature of dissolved phases at each deferration step to be determined and changes in Al-content of residual phases throughout deferration to be followed. It also demonstrated that Helmholtz coordinates correlate very well with changes in Fe-oxide mineralogy and are preferable to redness ratings when monitoring differential dissolution of Fe oxides through colour measurements. DRS is a powerful and sensitive technique for monitoring the dissolution of Fe oxides in soils.
A study has been made of a leaching process to remove iron from quartziferous industrial minerals using oxalic and sulphuric acid in a drum reactor. The experimental work was necessary because of the paucity of literature on the use of oxalic acid in the treatment of industrial minerals containing iron as an impurity. The positive effect of oxalic acid on the iron extraction yield is clearly observed during leaching in a drum reactor. Iron extraction yields of 35–45% are obtained on treating the quartz with 3 kg/t oxalic acid and 2 kg/t sulphuric acid at 90°C for 4–5 h. Under the same conditions but without oxalic acid the iron extraction yield ranges from 3 to 9%, depending on the sulphuric acid content. Chemical and mineralogical analyses were run on the ore to ascertain where the iron compounds occur on the different mineral components. These analyses were carried out on an as-is sample and on three other samples obtained by magnetic separation. The experimental results indicate that 52% of the iron is found in the mica fraction. These results explain why the maximum iron extraction yield is only 35–45%. A flow-sheet of the process is proposed together with a rough material balance in order to estimate oxalic acid, sulphuric acid and water consumption.
China clay is an important mineral, which is used in the manufacture of ceramics and refractory, as also in other industries. Mined China clay contains iron oxides and silicates as impurity; if present in excess of a threshold level, the impurities affect the commercial value of the products. Currently available processes for lowering the iron content in China clay to the desired level (<0.8%) are energy- and cost-intensive, not sufficiently flexible, and may cause environmental pollution. An alternative approach for iron removal consists in the development of a biotechnological process which is expected to be cost-effective, less complex and eco-friendly. We reported earlier that several fungi, especially Aspergillus niger, and their culture filtrates could leach sufficient amount of iron from a China clay sample; oxalic acid was found to be the most active component of the culture filtrate (Trans. Indian Inst. Met. 55 (2002) 1). We now report the rates of iron leaching from another China clay sample by oxalic acid and by the culture filtrate of A. niger NCIM 548 that was found to be the most active strain in our previous study (Trans. Indian Inst. Met. 55 (2002) 1). The iron-leaching rates increased with temperature (T) and followed biphasic kinetics. The effect of oxalic acid concentration (C), pH (H), solids concentration or pulp density (P), time and mode of agitation on the rate of iron leaching is described. The rate of leaching with oxalic acid (Rox) can be calculated theoretically from the following relationship: Rox∼(C)0.76(T)1.76(H)0.80(P)0.20 under the specified set of conditions. Using the same concentration of oxalic acid in A. niger culture filtrate, the relationship of the rate differed; this may be due to the influence of other metabolites present in the culture filtrate on the rate.
The presence of iron oxides in clay or silica raw materials is detrimental to the manufacturing of high quality ceramics. Although iron has been traditionally removed by physical mineral processing, acid washing has been tested as it is more effective, especially for extremely low iron (of less than 0.1% w/w). However, inorganic acids such as sulphuric or hydrochloric acids easily contaminate the clay products with SO42− and Cl−, and therefore should be avoided as much as possible. On the other hand, if oxalic acid is used, any acid left behind will be destroyed during the firing of the ceramic products. The characteristics of dissolution of iron oxides were therefore investigated in this study.The dissolution of iron oxides in oxalic acid was found to be very slow at temperatures within the range 25–60 °C, but its rate increases rapidly above 90 °C. The dissolution rate also increases with increasing oxalate concentration at the constant pH values set within the optimum range of pH2.5–3.0. At this optimum pH, the dissolution of fine pure hematite (Fe2O3) (105–140 μm) follows a diffusion-controlled shrinking core model. The rate expression expressed as 1 − (2 / 3)x − (1 − x)2 / 3 where x is a fraction of iron dissolution was found to be proportional to [oxalate]1.5.The addition of magnetite to the leach liquor at 10% w/w hematite was found to enhance the dissolution rate dramatically. Such addition of magnetite allows coarser hematite in the range 0.5–1.4 mm to be leached at a reasonable rate.
The dissolution of iron oxide (Fe2O3) using sucrose as the reducing substance in sulphuric acid solutions is described. The experimental runs were carried out in homogeneous (reduction of Fe3+ in solution) and heterogeneous (dissolution of Fe3+ from iron oxide and its reduction) tests: in the former case, the influence of acid and sucrose concentrations in the reduction of Fe3+ in solution was studied and several carbon sources were used.In the latter case, the influence of the main factors of dissolution of the iron from the mineral containing the iron oxide was studied; the factors investigated included acid and sucrose concentration, temperature and time of treatment. The results show how the presence of sucrose increases the iron extraction more than two-fold compared with the tests without sugar at the same acid concentration. This makes it possible to carry out a leaching process with a lower acid concentration.Full factorial design was used to plan the experimental work. The results show the potential application of this process in hydrometallurgical operations involving iron oxide dissolution (iron removal from industrial minerals, leaching of iron, etc.).
The efficiency of a biological bleaching process on a highly contaminated iron oxides kaolin was analyzed. The bio-bleaching method consists of two steps: first, the fermentation of a chemically-defined medium byAspergillus niger leads to a spent liquor which, in a second step, is employed as leaching agent for kaolin. In the leaching process 43% of iron oxides was removed when the kaolin was treated at 60C for 5 h and the whiteness index was increased to 67%. Extracellular enzymes were not responsible for leaching, which is basically due to organic acids produced during the fermentation.
Kaolin is the most extensively used particulate mineral in the filling and coating of paper. It improves paper appearance, which is characterized by gloss, smoothness, brightness and opacity, and of greatest significance, it improves printability. Paper is also filled with kaolin to extend fiber.The characteristics of kaolin that have the greatest influence on the quality of paper are the purity, rheology and particle geometry of the processed mineral. Generally, the most deleterious impurities for brightness of kaolin are iron oxide and titanium oxide minerals. The rheology of kaolin-binder-water suspensions at high solid: liquid ratios (as much as 65%) must be approximately Newtonian for efficient blade coating at speeds as great as 1300 meter/min. Particle geometry, defined as particle size, particle size distribution, particle shape and aggregate structure, has a dominant influence over the rheological character of kaolin slurries, as well as on the properties imparted by the kaolin to filled and coated paper.Increase in the aspect ratio of kaolin, as opposed to increase in surface area, exerts the dominant influence on the increase in low-shear viscosity. Although low-shear viscosities of undelaminated coating grades of kaolin show good correlation with surface area, the relationship breaks down for delaminated grades. Particle packing is believed to be the controlling parameter for viscosity at high rates of shear.Opacity, gloss, printability and, to a lesser extent, brightness of paper imparted by coating and filling with kaolin, are largely functions of particle size and particle size distribution. The strength of coated and filled paper generally decrease with decrease in particle size. An increase in coating void volume generally has a deleterious effect on strength.The principal commercial printing systems today are rotogravure and offset. Although other parameters are important, coating structures containing numerous voids generally give superior rotogravure printing, whereas smooth, relatively ink-impermeable surfaces are generally most favorable for offset printing.
Leaching studies of low-grade Joda manganese ore containing 24.7% Mn and 28.4% Fe were carried out at high temperature and atmospheric pressure using oxalic acid as reductant in sulphuric acid medium. The experiments were designed according to 24 full factorial design, and regression equations for extraction of manganese, iron and aluminum were determined from the data. All the significant main and interaction effects on extraction of Mn, Fe and Al have positive effect, except oxalic acid concentration and time interaction for extraction of Al. Oxalic acid concentration has strongest effect on extraction of Mn, whereas temperature and time have strongest effect on extraction of Fe and Al, respectively. 98.4% Mn and 8.7% Fe were extracted from −150+105 μm ore with 30.6 g/l oxalic acid, 0.543 M sulphuric acid concentration at 85 °C in 105 min.
The light-induced dissolution of the iron oxide, lepidocrocite (γ-FeOOH), has been investigated and found to be greatly enhanced in the presence of citrate. A conceptual model of the dissolution process is presented and validated through studies of citrate adsorption to lepidocrocite, net iron oxide dissolution under a variety of conditions, and solution phase redox reactions. The initial dissolution rate is directly related to the concentration of the surface bound ferric citrate and the first order rate constant for the photodissolution process is very similar to that found for the photodissociation of soluble ferric citrate. Dissolution most likely occurs through direct excitation of charge transfer bands of the surface bound ferric citrate. At low pH (pH 4.0), a constant rate of dissolution is observed while at higher pH (pH 6.5 and 8.2), the dissolution rate decreases on continued photolysis. This decrease is due to (1) an oxygen-dependent deactivation process occurring at the surface and (2) loss of photo-produced iron from solution by “ligand-like” adsorption of soluble iron citrate complexes by the colloidal iron oxide. Superimposed on the dissolution process at these higher pH is a rapid oxidation-reduction cycle involving solution phase iron species with the reduction step induced by photodissociation of ferric citrate complexes and the oxidation step controlled by the formation of ferrous citrate.
We report a novel protocol to prepare titania hollow nanospheres of size about 28 ± 1 nm with micelles of asymmetric triblock copolymers. The hollow particles exhibit unique electrochemical properties in lithium ion rechargeable batteries such as high capacity, very low irreversible capacity loss, and high cycling performance.
Low- and high-defect kaolinites mechanochemically activated for different periods of time have been treated with sulfuric acid solution. These modified materials were analyzed using a combination of X-ray diffraction, thermogravimetry, chemical analysis, diffuse reflectance Fourier transform infrared spectroscopy, as well as specific surface area and pore size distribution measurements. In addition to the mechanochemically amorphized part, the disordered and the adequately distorted phases also reacted with sulfuric acid. The specific surface areas of the leached samples of the partially or the completely amorphized materials were found to be greater than those of the thermally amorphized ones. The acid treatment results in a greater total pore volume for the partially amorphized materials than for the totally amorphized mineral. The partially amorphized high-defect kaolinite was proved to be more soluble than the low-defect kaolinite under similar conditions.
a (108M180 no'lu proje) teşekkür ederiz. Ayrıca cevherlerin temininde yardımları ve destekleri için ÇİMSA A.Ş. yetkililerine, deneysel çalışmalarında teknik desteklerinden dolayı SDÜ Jeotermal Enerji
- Teşekkür Desteklerinden Dolayı
TEŞEKKÜR
Desteklerinden dolayı TÜBİTAK'a (108M180
no'lu proje) teşekkür ederiz. Ayrıca cevherlerin
temininde yardımları ve destekleri için ÇİMSA
A.Ş. yetkililerine, deneysel çalışmalarında teknik
desteklerinden dolayı SDÜ Jeotermal Enerji,
Yeraltısuyu ve Mineral Kaynakları Araştırma ve
Uygulama Merkezi personeline ve mineralojik
analizlerdeki yardımlarından dolayı Yrd. Doç.
Şemsettin Caran'a, deneysel çalışmalardaki yardımları için Müh
- Dr
Dr. Şemsettin Caran'a, deneysel çalışmalardaki
yardımları için Müh. Mustafa Şahin ve Müh.
Kaolenlerin Safsızlaştırılmasında Kimyasal ve Biyolojik Yöntemlerin İncelenmesi
- Kaynaklar Akçıl
- A Tuncuk
KAYNAKLAR
Akçıl, A. ve Tuncuk, A., 2006; " Kaolenlerin
Safsızlaştırılmasında Kimyasal ve Biyolojik
Yöntemlerin İncelenmesi ", Kil Bilimi ve Teknolojisi
Dergisi, 1, 59-69.
Biyoliç Yöntemiyle Endüstriyel Hammaddelerden Safsızlıkların Uzaklaştırılmasının Araştırılması
- V İ Arslan
Arslan, V.İ., 2008; " Biyoliç Yöntemiyle
Endüstriyel Hammaddelerden Safsızlıkların
Uzaklaştırılmasının Araştırılması ", (Doktora Tezi),
Çukurova Üniversitesi Fen Bilimleri Enstitüsü.
Purified Quartz and Process for Purifying Quartz " , United States Patent
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- R D James
Loritsch, K.B. ve James, R.D., 1991; " Purified
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States Patent, Patent Number : 4,983,370.
Introduction to Probability and Statistics Principles and Applications for Engineering and The Computing Sciences Design and Analysis of Experiments Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri
- J S Milton
- J C Arnold
Milton, J.S. ve Arnold, J.C., 1995; " Introduction
to Probability and Statistics Principles and
Applications for Engineering and The Computing
Sciences ", Factorial Experiments, 14, 604-655.
MINITAB 15, 2009; Statistical Software.
Montgomery, D.C., 1991; " Design and Analysis
of Experiments ", 3rd ed., Wiley, New York.
Özensoy, E., 1982; " Teknolojik ve Bilimsel
Araştırmalarda Modern Deney Tasarımcılığı
ve Optimizasyon Yöntemleri ", M.T.A. Enstitüsü
Yayınları Eğitim Serisi, 24, 26-35.
The Role of Bacterial Alteration in Whitening and Iron Removal from Georgia's Commercial Kaolin Clays
- E Shelobolina
- S M Pickering
- J E Kogel
Shelobolina, E., Pickering, S.M. ve Kogel,
J.E., 2002; " The Role of Bacterial Alteration in
Whitening and Iron Removal from Georgia's
Commercial Kaolin Clays ", SME Annual Meeting,
Phoenix, Arizona.
The Economics of Kaolin
- Roskill
Roskill, 2006. The Economics of Kaolin, 12th ed. Roskill Information Services, Ltd.
Industrial minerals in Arizona's paint industry. Open-file Report. Arizona Department of Mines and Mineral Resources
- K A Philips
Philips, K.A., 1989. Industrial minerals in Arizona's paint industry. Open-file Report.
Arizona Department of Mines and Mineral Resources, pp. 1-8.
Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri
- E Özensoy
Özensoy, E., 1982; " Teknolojik ve Bilimsel
Araştırmalarda Modern Deney Tasarımcılığı
ve Optimizasyon Yöntemleri ", M.T.A. Enstitüsü
Yayınları Eğitim Serisi, 24, 26-35.
Spectroscopic control of iron oxide dissolution in two ferralitic soils
- N Malengreau
- A Bedidi
- J P Muller
- A J Herbillions
Malengreau, N., Bedidi, A., Muller, J.P., Herbillions, A.J., 1996. Spectroscopic control of
iron oxide dissolution in two ferralitic soils. Eur. J. Soil Sci. 47, 13-20.
Processo per la rimozione del ferro da concentrati di caolino. Quarzo ed altri minerali di interesse industriale
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- B Paponetti
- A Marabini
- B Passariello
Toro, L., Paponetti, B., Marabini, A., Passariello, B., 1990. Processo per la rimozione del
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